The process of transferring charged toner particles from an image bearing member marking device (e.g. photoreceptor) to an image support substrate (e.g., sheet) involves overcoming cohesive forces holding the toner particles to the image bearing member. The interface between the photoreceptor surface and image support substrate is not always optimal. Thus, problems may be caused in the transfer process when spaces or gaps exist between the developed image and the image support substrate. A critical aspect of the transfer process is focused on the application and maintenance of high intensity electrostatic fields in the transfer region for overcoming the cohesive forces acting on the toner particles as they rest on the photoreceptive member. Careful control of these electrostatic fields and other forces is required to induce the physical detachment and transfer-over of the charged toner particles without scattering or smearing the developer material. Mechanical devices that force the image support substrate into intimate and substantially uniform contact with the image bearing surface have been incorporated into transfer systems. Various contact blade arrangements have been proposed for sweeping the backside of the image support substrate, with a specified force, at the entrance to the transfer region.
Xerographic systems use a Transfer Assist Blade (TAB) to flatten print media onto the photoreceptor to ensure uniform transfer of the toner to the sheet. With a moving process the TAB must be timed to touchdown and lift off respectively as close to the lead edge and trail edge of the sheet as possible in order to maximize the portion of the sheet having uniform toner transfer. TAB timing is affected by variations in process velocity, mechanical geometry, software iteration delays, image-to-sheet registration and sheet thickness, cut size and shrinkage. At present TAB timing is calibrated for the fleet based on observations with high-speed video on sample systems. In order to ensure that the TAB does not touch the photoreceptor (which would be harmful) the reference timing is set conservatively, accounting for these variations. Individual system calibration in the field is impractical because of the requirement for high-speed video.
One methodology for adjusting the transfer assist blade timing requires a time consuming manual process wherein the user is required to make trial-and-error input to the system, with visual observations of the result. This is a frequent adjustment which is required when the transfer assist assembly, or its replaceable blade element becomes worn or damaged, as it often does due to constantly coming into contact with moving print throughput (paper). The user is required to manually record specified non-volatile memory (NVM) data then change the NVM settings to cause the trail edge timing of the transfer assist blade to be delayed. This causes the blade to contact the photoreceptor and acquire a small amount of toner placed on the photoreceptor by the system. The user repeatedly checks for marks on the lead and trail edges of the back side of a test print to determine that the timing adjustment is as specified for the product. The user makes a test print, evaluates the print, makes a data entry to the system, and makes another test print, thus beginning a cycle of events concluding when the result specified for the product is obtained. The user must then return the trail edge timing to the original values, manually recorded earlier in the set up. The number of user interactions is high and time consuming. The time to perform this exercise represents considerable cost to the company measured in technical service hours.
There is an unmet need in the art for automated TAB timing calibration systems and methods that overcome the above-mentioned deficiencies and others.